By Jacob Shurba, intern at the American Bald Eagle Foundation
** Warning, there are photos of dead and dying birds in this post. **
As a wildlife rehabilitator and disease ecologist, I am no stranger to seeing animals in some sort of peril, especially birds. Besides the normal everyday struggles like predation and food shortages, birds are up against many anthropogenic (human made) factors as well. These include power lines, soccer nets, and toxins such as lead. Lead in particular is a major threat to many birds, including waterfowl and bald eagles. As a disease ecologist, it is easy to tell when a bird is suffering from lead toxicity – but to someone who does not look at toxicity for a living, symptoms of lead poisoning can be subtle. I would like to discuss lead toxicity, what it looks like, how it happens, and what you can do, as an average Joe, to help protect the species at risk.
The scientific definition of lead poisoning, also known as lead toxicity, from the US Geological Survey’s (USGS) Field Handbook of Wildlife Diseases is, “Lead poisoning is an intoxication resulting in absorption of hazardous levels of lead into body tissues.” While the definition seems clear-cut, how does lead poisoning affect birds, and what do symptoms look like? There are a select few ways that toxicity occurs, though it is mostly caused by the ingestion of an object that is either straight lead, or contains lead in some way.
The truly nefarious thing about this toxin is that it can remain in the environment for a prolonged period, which is how it is introduced to most waterfowl. Even though lead shot was banned from being used in waterfowl hunting in 1991, pellets from before that time still sit at the bottom of marshes and ponds just waiting to be ingested by unsuspecting waterfowl. These birds are not actively searching out the lead pellets, rather they eating things out of the mud and will accidentally pick up the pellets while they eat. In the case of eagles and other raptors such as condors, the lead is ingested in a very different way. While lead shot may be banned for the hunting of waterfowl, it isn’t banned for other types of hunting. So, a hunter may shoot an animal, gut it and leave the guts in a pile in the woods for scavengers to eat.
The fragmented lead shot is usually remaining in the gut pile, and when eagles and other birds come down to eat the guts, lead is ingested and the poison begins to work its deadly magic. It is not difficult for scavengers to accidentally swallow these fragmented bits of lead. In a study performed from 2002-2004 by the Peregrine Fund, they discovered that in 38 deer carcasses, five of them contained over 200 lead fragments, five contained 100-199 lead fragments, and five contained 10-100 lead fragments. They went on to take x-rays of 20 different gut piles and found that 18 of them contained lead fragments.
There are a few ways of identifying lead poisoning symptoms in birds. In the field, lead poisoned birds generally won’t fly away when approached. However, if they do attempt flight one will notice that they are weak and are unable to fly long distances, or they fly very erratically and do not land very well. In the case of waterfowl, they begin to develop an abnormality where their wings form a roof shape over their backs. The birds are also generally lethargic and have a lot of trouble eating and drinking normally. This begins to display itself in something called “hatchet breast” which is when the bird loses so much muscle and fat that the breast bone (or keel) is visible through the feathers, looking like a hatchet blade.
Although lead poisoning seems to be an ominous feat there is a glimmer of hope, and that’s where humans play in. The bald eagle, besides being our national symbol is also a huge conservation success story which shows that if we work together, we can bring a species back from the brink of extinction. I’m not saying that the bald eagle is again in danger of going extinct, but if this problem isn’t solved, then that is a distinct possibility. So, what do we do?
While there are many different choices, we will focus on the ones that are easy and cheap to implement. The first and by far the largest change one can make, is a change from lead shot to a different type of shot. Don’t use lead shot. Copper and steel shot are both excellent alternatives to lead, since neither have negative side effects if ingested. The other thing that can be done is removing gut piles from the woods after you’ve dressed your animal. For any fisherman, an easy thing to do is be mindful of what sort of tackle you are using. Make sure that you are using tackle that doesn’t have any lead, there are many places that sell non-lead fishing tackle. If we try to implement these things as well as others for a more conservation based life style, we can keep this beautiful bird soaring through the sky where they belong.